


Let's Kill Tonight

by myn_x



Series: Daichi Rarepair Week Feb. 11-17 2017 [2]
Category: Haikyuu!!
Genre: M/M, Modern Fantasy, Multi, Siren!Iwaizumi, Siren!Oikawa, Swimmer!Daichi
Language: English
Status: Completed
Published: 2017-02-16
Updated: 2017-02-16
Packaged: 2018-09-24 21:19:42
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,609
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9787400
Author URL: https://archiveofourown.org/users/myn_x/pseuds/myn_x
Summary: This is for Day 2 ofDaichi Rarepair Week, which was on Feb. 12Prompt: Stars /Memes/ Modern fantasy AU





	

**Author's Note:**

> i know there's a difference between sirens and mermaids, but i chose to use "siren" because it's not a gendered noun like "mermaid" or "merman" are. it also just...sounds better. so i use "siren," but think of the half-human, half-fish kind xD
> 
> this doubles as an experiment in pronoun usage, so just be aware of that as you read!
> 
> as always, infinite thanks to abby for giving me the confidence to finish this (๑・ω-)～♥”
> 
> oh, and give [this song](https://www.youtube.com/watch?v=uu2XSQgdQDY) a listen ;D it reminds me of Oikawa

The lagoon has been Daichi’s favorite place to swim for as long as he can remember. He first came as a child, when it was just him and his mother, who had taught him how to trust the water.

Then when she remarried and it didn’t work, the property, and most importantly the lagoon, became his refuge -- a slice of heaven on an island full of mostly empty beach houses.

The university that had recruited Daichi sent scouts to watch him compete, his form and swim times attracting more attention than he cared to receive, but their offer was one he couldn’t refuse. Their swim team had gone to nationals the previous year, meaning he had somewhat of a chance of going with them (he hadn’t thought as far as the Olympics yet, but there was that possibility too), and it was only a prefecture over. Daichi had long decided to spend as many weekends on the island as he could.  

He’s in his element as he steps down from the wooden stairs that lead back up to the house; his wetsuit feels like a second skin, and the hard grittiness of the sand between his toes makes him feel at peace.

Daichi’s anticipation rises as he gets closer to the small waves that crest and tumble, and beyond to the almost smooth surface that reflects the mess of stars above him. The moon hides her face tonight, and it’s as if he’s walking directly into the night sky.

He shivers with his first steps into the water, feet sinking a little into the softer sand. Once he reaches a depth where the water laps against the tops of this thighs, he inhales and dives forward, and the water welcomes him in like an old friend.

As a distance swimmer, his focus has always been his stamina. He may not have to deal with strong currents like he would if swam at the beach a mile or two away, but the lagoon water has a will of its own, and he can feel tiredness weighing him down not long into his laps.

The edge of the lagoon where coral separates it from the sea is choppier, and Daichi usually stays away from it. But the ocean seems to call to him, a low, somber humming echoing in his ears, and he finds himself cutting through the water toward a dip in the barrier that leads to darker waters.

Something slick and cold drags him down as soon as he’s past the highest coral, and it breaks the spell. He tries to dislodge it with a kick, but whatever it is, it’s stronger than him, and he’s being dragged down, arms flailing in a futile attempt to keep himself from drowning.

Now sightless, the only thing he’s aware of is how cold it is -- and then he remembers the thing latched to his ankle, he reaches for it, shrinking back once he realizes it’s a human hand.

Daichi struggles harder, panic fully settling in. He’s outside of the safety of the lagoon, with some humanoid creature trying to drown him; his arms and legs are past exhausted, lungs burning for air. He chokes on the water, wasting precious air that escapes in bubbles -- the instinct to yell for help is too strong for logic. He can’t tell which way is up or down or sideways, and he can’t tell how much time has already passed. He can’t even tell if he’s about to pass out because it’s already pitch black. All he knows is that he’s drowning, and he doesn’t even have the mind to appreciate the irony of it.

Only the stars above will witness his death.

When Daichi opens his mouth again, he swallows more water, but he isn’t choking. Aside from whatever’s anchoring him below the surface, he’s...fine. He thrashes again, but the thing doesn’t let him go. He suspects he’s already dead.

Daichi hears another sound, a sort of musical trilling, and it seems...annoyed, for lack of a better word. He didn’t even know pure sound could possess emotion. Then he picks up on a second, lower sound, what must be a response. The two noises come from below him and to his left, the  one continuing to complain while the latter replies with increasing exasperation. It’s an odd, haunting song, eery as it is alluring.

And miraculously, he’s free.

There’s no moon to tell him where the surface is, so he doesn’t know which direction to kick, but at least he isn’t drowning. The only feeling of wrongness is a vague discomfort in his chest. He opens his mouth again and nothing happens, then sucks in water through his nose with the same result. Huh. He’s always had some of the best records for breath-holding but this is just insane.

A darker patch of water moves in front of him, and he clumsily backpedals, but then hands wrap around his throat. But they don’t squeeze. Instead, the fingers slide up his neck just below his ears, and then they’re gone.

Something tugs at the back of his suit and then he’s being dragged deeper, he assumes. But then he breaks the surface, and he takes a moment to suck in precious air before spinning to locate the reef.

Adrenaline keeps Daichi from passing out despite his exhaustion and the piercing cold -- he speeds toward the lagoon, wasting no energy on anything other than swimming.

It strikes him that he’d never swim again if it meant he could be on dry land at this very moment.

Fear scatters his thoughts of everything but escape; he needs to get away from whatever the fuck just tried to drown him and be out of the water, period, and he’s in such a frenzy to return to safety that he doesn’t notice he’s being pursued.

It’s the voice that carries over the water’s choppiness that stops him cold.   

“You’re the first human I’ve tried to drown, and I can’t believe you had the nerve to not die!” The voice has the same petulant tone as one of the sounds he heard underwater. “But you’re not even human, are you?”

He turns around to locate the source of the voice. “E-excuse me?”

All he can see are two indistinct shadows bobbing above the surface. One of them slips below the surface and then pops up in front of him in less than the time it takes him to blink saltwater out of his eyes.

“What are you, eh? Where’s your tail?”

The creature is pretty, dangerously so, in the starlight. It appears human but there’s a pearlescent, scaly sheen to its cheeks and the tops of his shoulders that reminds Daichi of a tropical fish. Its reflective eyes are framed by long lashes that sparkle with seawater, and long, curved gashes ( _gills_ , Daichi realizes) almost encircle its neck. Water drips from the ends of its dark, wavy hair, which doesn’t quite hide its pointed ears.

Daichi is too stupefied by the siren’s beauty to comprehend its words. “My what?” His limbs still, and he sinks a little before remembering that he has to actively work to keep himself afloat.

The second shadow turns out to be a siren, too, and it’s just as captivating. It breaks the surface next to the first; its hair is shorter and spiky, and the angle of its eyes are different as well, but otherwise, it possesses the same ethereal features as the other.

“He’s got gills, so he isn’t human, but he doesn’t have a tail,” it says. The timbre of its voice matches the other, impatient half of that otherworldly song. “I’ve only heard of this happening, but he might be a hybrid, Oikawa.”

“Iwa-chan, don’t be absurd.”

Daichi looks back and forth between the pouting creature and its scowling companion, their words fading to a faint buzz in his ears. His muscles are stiff with coldness and fatigue, and he doesn’t realize he’s sinking again until the blackness pulls him under -- at least his second descent into the deep is gentler than the first.

 

~

 

A cold, wet finger prods his cheek. “Hey! Did you finally decide to die?”

Daichi opens his eyes. The sun peeks above the horizon, and the siren, the one called Oikawa, hovers over him. Daichi’s legs are still in the water, which ebbs and pools around him, but his back is pressed against solid ground. He’s never been more relieved to return to the sand, and he digs his fingers into it, rooting himself.   

"You passed out in the middle of our conversation," Oikawa continues as it pokes him in the chest. "How rude!"

“Oikawa…” The other siren lies a few feet away, back to the shore and elbows in the sand. It doesn’t look away from the sunrise as it gently scolds the other.

“Iwaizumi Hajime! Let me finish,” Oikawa hisses. The scaly pattern on its cheeks glow red as it refocuses its attention on Daichi. "I’ve been waiting for you to wake up for hours, half-human. Aren’t you going to thank me? I _saved_ you."

"You did try to kill me first." Daichi’s voice is ragged, probably from swallowing so much seawater. He rolls over and edges away from the water, putting a little distance between himself and the siren; in the faint dawn light, Daichi could see its sharp teeth.  

Iwaizumi clears his throat. "Which you haven't apologized for."

Daichi gives Oikawa a pointed look. “ _Thank_ you, Iwaizumi.”

“You and the half-human barely know each other and you’re already ganging up on me!”

Daichi isn’t sure how mythological creature etiquette works, but the epithet makes his stomach twist. He snaps, “My name’s Sawamura Daichi, but Daichi is fine, thanks.”

“Daichi,” Oikawa repeats, turning up its nose. “I like ‘half-human’ better.”

Its forked tail fin flicks and catches Daichi’s attention. From where the siren lies at the edge of the water, its head propped on the heels of its hands, he can see the rest of its body. Its skin has blue-green undertones, with more random patches of colorful scales on its chest, sides, and back, and its sapphire tail shimmers in the sun, dorsal fin fluttering in the wind.

He wonders how something so beautiful can be so deadly. “Why did you even do it?”

“Try to drown you? Revenge, I suppose,” Oikawa says flippantly.

“I never did anything to you.”

“I thought you were of the kind who did.”

“That’s hardly fair. You attempted to drown me, but based on my observations your kind isn’t inherently dangerous.” The lie tastes like salt on Daichi’s tongue. He means Iwaizumi, but he still doesn’t fully trust either of the creatures.

As much as he fears the sirens, though, he’s enjoying their company. He wetsuit is nearly dry, and he pulls his knees to his chest to stave off the chilly breeze.

“It wasn’t like I invited myself over for tea,” Oikawa huffs. It twists to show Daichi the ugly, jagged scar on its right flank that runs from its hip to the middle of its tail, through one ruined pectoral fin. Then it leans back to lie with its arms crossed behind its head, closing its eyes. “They caught me and wanted to do nefarious things with my body. They would have gutted and filleted me, put me on display, if I hadn’t escaped.”

“Sirens don’t try to kill people very often,” Iwaizumi says. It tips its head toward Oikawa’s resting figure. “This idiot is just...he’d be lost without me.”

“So you’re both guys?” Daichi blurts. Where Oikawa’s tail is the deepest blue, Iwaizumi’s is a rich emerald.

“Uh, I guess?” Iwaizumi shrugs. “Yeah, so after his run-in with those humans, I realized I couldn’t leave him by himself, and in the time it took him to heal we’d bonded.”

“And then?”

“And then, we kinda just drifted wherever, then found this island and this is where we’ve been, give or take a few miles. I’ve had to keep Oikawa away from more populated areas because of his…obsession with people.”

“You mean because he was angry about what happened, and wanted to return the favor.”

“Yeah, and you were right in his path. After years of built-up rage, he was quick to lash out at someone he thought was human. You smell human more than anything else, but without whatever siren blood you have, you’d be dead.”

Iwaizumi’s words chill him, and the goosebumps that crop up on his arms and legs make him want to get back in the water, to where it feels a little warmer. He doesn’t really know why he risks getting closer to them -- well, to Oikawa.

And the absurdity of it all (almost dying, discovering he’s part siren and can breathe underwater, staying to talk with living, breathing sirens) makes him dizzy. A chuckle escapes in a low rumble, and then it crescendos into all-out, side-splitting laughter.

Iwaizumi turns to look at him in alarm, while Oikawa only side-eyes him. “Does something amuse you, Daichi?” the former asks.

Between the exhaustion and his apparent disconnect from reality, he can’t process all of the things he’s feeling -- confusion, fear, disbelief, things he has no name for. “I can’t help but feel--” he pauses to wheeze another laugh, “as if I’m dreaming and that none of this is real.”

Before he’s even done speaking, Oikawa is splashing toward him with an unreadable but determined expression. Daichi backs away from him, but he bumps into Iwaizumi, who grips his forearms gently. He’s shaking, laughs replaced by shallow, shaky breaths. Once he’s close enough, Oikawa takes his hands. They’re warm from where they were behind his head, so Daichi doesn’t pull away.

“You’re here, I’m here, and Iwa-chan’s here,” Oikawa says in a low voice. “You can touch me, if you’d like, in case you don’t believe me.”

He drops Daichi’s hands, and Iwaizumi lets him go. He sits between the two of them, still trembling, but he’s not afraid. Oikawa’s eyes are locked on his, and Iwaizumi’s solidness behind him is reassuring. Oikawa shifts so that his tail is close enough for Daichi to touch, if he chooses to reach for it. This close, his scar looks so painful.

“Does it hurt?” Daichi asks quietly.

Oikawa cocks his head. “It doesn’t.”

It must take a lot, for Oikawa to trust him like this. Daichi runs his fingers along the smooth, iridescent scales of his tail. He pauses at the scar, and when Oikawa doesn’t object, he smooths a hand over its roughness. Oikawa hums, and it has a musical quality not unlike the song that lured him out to sea, but Daichi doesn’t feel compelled. It’s the sound of wind chimes and the rush of a whitewater river. It’s the sound of peace.

Oikawa’s eyes drift shut as Daichi moves his fingertips along his tail, starting where it connects with his torso and stopping where the old wound ends. He repeats the motion, again and again, as if he’s in a trance. Iwaizumi brushes his cheek, to catch tears he wasn’t even aware were falling.

“I--I have to go,” Daichi says. The song fades, and they look up at him as he stands and backs away. “Er, thank you. For that.”

“You’re a fickle creature, Sawamura Daichi,” Oikawa says evenly. He pouts at him, and Iwaizumi looks on affectionately. “You don’t thank me for saving your life, but you do thank me for a simple song.”

Daichi can’t explain any of the emotions that wash over him. He can only hope they aren’t the product of a glamour, since he’s too scared to ask if they are. “I need to get some sleep, but I’ll be back out later. Will you be here?”

Oikawa looks away. “I don’t know.”

Iwaizumi huffs and rolls his eyes. “Get some rest, Daichi.”

 

~

 

Daichi sends his mother a text as soon as he gets inside.

_We need to talk. Can we meet?_

Not waiting for a response, he sets it back on the counter, face down.

After he draws a bath, he stands before the tub, contemplating the water. He runs his hands over his neck, searching for the gills that kept him from dying. The skin is smooth.

In the bath, he dunks his head underwater. But his lungs reach their limit and scream for air, not water. He breaks the surface, pressing his fingers to his eyes. Maybe it was a dream (a nightmare, he corrects himself) after all.

 

~

 

By early evening Daichi’s stepping down into the sand again. He sets his shoulders. They’ll be there, or they won’t.

He doesn’t have to wait long after stepping into the water before two heads pop up in the middle of the lagoon, one after the other.

Daichi can hear Oikawa’s indistinct complaining. As they get closer, he can make out his words. “Daichi! Took you long enough!”

He raises a brow in response. There’s no way he’d be able to make this up, even in the most ludicrous of dreams, he finally settles on accepting this weird turn his life has taken. “Good evening to you too.”

Iwaizumi laughs, and it’s as pretty as, if not prettier than any of their songs.

“Hurry up and get in, Daichi,” Oikawa whines. “I wanna show you something.”

“Only if you promise there’s no drowning involved.”

“I think he got that out of his system last night.”

“Iwa-chan!” Oikawa turns his glare on his partner, then turns back to Daichi. “And you! You can’t even drown, so what does it matter!”

“That’s my only condition. No weird shit.”

“Alright, alright, please get in!”

“You never say ‘please’ to me,” Iwaizumi grumbles. He winks at Daichi, who laughs as he wades over to where they wait.

Oikawa ignores Iwaizumi; his impatience is nearly tangible. “Come on, come on!”

They dip underwater and lead Daichi to the edge of the lagoon, but as they approach the barrier, trepidation slows him down.

Iwaizumi senses his fear and hesitation. He turns back, finding his hand beneath the water and squeezing gently. “It’s a lot to ask, but please trust us,” he says. “We’ve got you.”

Oikawa looks on from beyond the coral. Daichi remembers how he soothed him when everything became too much, and the feelings he couldn’t name because he didn’t, and still doesn’t have the words. He knows deep down they won’t do anything to put him in danger; his instincts tell him that, and they tell him to swim.

Iwaizumi doesn’t let go as they press forward and into the sea.

The three stop a not far beyond the coral shelf. “One second,” Daichi says. He untangles his hand from Iwaizumi’s, letting himself sink beneath the surface. Opening his mouth, he sucks in ocean water, and breathes.

He rises back to the surface, and the sirens eye him with puzzled expressions.

“When I took a bath earlier,” he starts, reaching to feel for his gills, “I couldn’t breathe the water.”

The slits in his neck are smaller than Iwaizumi’s and Oikawa’s, which he supposes is a result of his mixed blood, as is their selectiveness.

“It must have something to do with the water quality,” Iwaizumi muses. “Sirens don’t do too well in water that’s been tampered with, so your gills will probably only appear if you’re in pure water that flows naturally.”

“Then I won’t be able to breathe pool water either then,” Daichi says with a laugh.

“I don’t know why you would want to.” Oikawa swims back and forth in front of Daichi. “Now, I want you to close your eyes and hold your arms out.”

“Okay.” Daichi does as he’s told, biting back the complaint that rises in his throat. It’s different, swimming in the almost-open ocean, and the muscles in his legs are already protesting when he hears a whistle.

Almost immediately, Daichi feels smooth, rubbery objects bump under each arm. His eyes fly open in surprise, and he realizes they’ve brought him to swim with dolphins.

He can’t contain joy the animals bring him, and he turns to beam at the pair as Oikawa yells to hold on tight. The slick animals tug him forward, and they’re fast, all power and muscle, tails propelling them fast enough that when he looks for them, Oikawa and Iwaizumi are specks bobbing on the waterline.

Daichi doesn’t hear the second whistle, but the dolphins bring him back to the sirens, who wait with smiles of their own. The dolphins nudge him with their snouts, clicking and chirping with affection before Oikawa swims away to see them off.

“It was his idea, you know,” Iwaizumi says. They both watch as Oikawa plays with the powerful animals, who jump over him and squirt water in his face. He laughs and splashes them back, and it’s so adorable that Daichi has to look away.

“He’s not good at apologizing, but this is his way of saying sorry.” Iwaizumi offers Daichi his arms, since the waves have gotten stronger.

Daichi clings to him gratefully, finally able to rest his legs. “I’d say he’s very good at apologizing, actually.”

Iwaizumi laughs, and then Oikawa swims back over to them. The dolphins are gone.

“What are you two plotting?”

“Nothing,” they say, and laugh again. Oikawa’s eyes are full of suspicion, but there’s an equal amount of affection in the look he’s giving them.

By the time they return to the lagoon, Daichi’s favorite place, it’s just the three of them beneath the stars. It’s surreal enough to be a dream, but Daichi has never felt more alive.

  


**Author's Note:**

> [tumblr](http://ohmykokuroo.tumblr.com) || [other tumblr](http://zeppellii.tumblr.com) || [twitter](https://twitter.com/lovedeluxxxe)


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